Selective hydrogenation catalysts

ABSTRACT

CATALYSTS SUITABLE FOR THE SELECTIVE HYDROGENATION OF DIOLEFINS TO MONO-OLEFINS ARE PREPARED BY CONTACTING A GROUP VIII METAL SURFACE E.G., NI OR PT, WITH A GROUP V COMPOUND OF FORMULA X3M, WHERE X IS AN ORGANIC RADICAL, H OR C1 AND M IS AN ATOM OF PHOSPHORUS, ARSENIC OR ANTIMONY SO THAT THE GROUP V ELEMENT OR COMPOUND IS ABOSRBED ONTO THE METAL SURFAC. PREFERRED GROUP V COMPOUNDS ARE: (C6H5)3P, ET3P, (NC4H9)3P, TRIOCTYL PHOSPHINE, TRICYCLOHEXYL PHOSPHINE AND TRIISOPROPYL PHOSPHINE. IN A MODIFICATION A COMPOUND OF FORMULA.   $2P-(CH2)XCH2-P$2   WHERE X IS O OR AN INTEGAR AND $ IS PHENYL GROUP MAY BE EMPLOYED.

A K. G. ALLUM E TAL 3,642,658 SELECTIVE HYDROGENATFON CATALYSTS Feb. 15, 1972 Filed Dec. `19, 1968 3 Sheets-Sheet 1 ATTORNEY;

Feb. 15, 1972 K. G. ALLUM El' AL SELECTIVE HYDROGENATION oAfrALYsTs Filed Dec. 19, 1968 3 Sheets-Sheet 2 www www5? Feb. 15, 1972 Filed Deo. 19, 1968 K. G. ALLUM Er ALv Y 3,642,658 SELECTIVE HYDROGENATION cA'ALYsTs l 5 Sheets-Sheet 8 United States Patent C1 ice 3,642,658 SELECTIVE HYDROGENATION CATALYSTS Keith George Allum, Bagshot, Christopher John Leonard Metcalfe, Sunbury, and Daniel John Thomasson, Hanworth, Feltham, England, assiguors to The British Petroleum Company Limited, London, England Filed Dec. 19, 1968, Ser. No. 785,219 Claims priority, application Great Britain, Dec. 21, 1967,

8,033/ 67 Int. Cl. C07c 11/0 U.S. Cl. 252--431 P 11 Claims ABSTRACT OF THE DISCLOSURE Catalysts suitable for the selective hydrogenation of diolefns to mono-olefins are prepared by contacting a Group VIII metal surface e.g., Ni or Pt, with a Group V compound of formula X3M, where X is an organic radical, H or `Cl and M is an atom of phosphorus, arsenic or antimony so that the Group V element or compound is absorbed onto the metal surface. Preferred Group V compounds are: (C5H5)3'P, EtgP, (nC4H9)3P, trioctyl phosphine, tricyclohexyl phosphine and triisopropyl phosphine. In a modification a compound of formula where x is 0 or an integer and 9S is phenyl group may be employed.

This invention relates to the preparation of Group VIII metal catalysts.

Group VIII metals are well known catalysts, particularly for hydrogenation and dehydrogenation reactions. The fresh metal surface has a high activity, and is, for example, capable of hydrogenating any unsaturated hydrocarbon including aromatics. For some reactions, however, the catalyst is required to have selective activity. In the field of hydrogenating the catalyst may be required to hydrogenate oleiins or acetylenes without hydrogenating aromatics and within the field of olen hydrogenation there is also a further selectivity possible, the selective hydrogenation of diolefins to mono-olefns, leaving both monoolefins and any aromatics untouched.

The present invention is concerned with the treatment of a Group VIII metal surface to modify its catalytic activity. v

According to the present invention a method of preparing a catalyst comprises contacting a Group VIII metal surface with a compound of an element of Group V so that the Group V element or compound is adsorbed onto the metal surface, the Group V compound having the general formula X3M where X is an organic radical, a hydrogen or halogen atom, the X radicals being the same or different, and M is an atom of phosphorus, arsenic, antimony or bismuth; and in the case where M is phosphorus at lease one of the X radicals may be where n is zero or an integer from 1 to 20` and where R is a C1 to C20 hydrocarbon radical, in addition to those specified above, and with the proviso that when M is bismuth the X radicals are hydrogen atoms or C1 to- C6 hydrocarbon groups and may be the same or different.

The preferred Group VIII metals are those of the nickel triad i.e. nickel, palladium and platinum, particularly nickel. The Group VIII metal is preferably carried on a support in a known manner. Any of the known catalysts supports may be used, for example natural or synthetic refractory oxides of elements of Groups II to IV of the Periodic Table particularly silica and/or alumina, natural or synthetic refractory silicates particularly alumino-silicates and/or magnesium silicates such as sepiolite, and activated carbon.

The Group VIII metal should be in elemental form before contact with the compound of Group V and, again, any known method of applying Group VIII metal compounds to a support and reducing the compounds to elemental metal may be used. Preferably nickel formate in ammonia solution is used to impregnate a support and the nickel formate is reduced at 200-550" C. in a stream of inert gas or hydrogen. The Group VIII metal content of a supported catalyst may be from 0.1 to 50% wt. by weight of total catalyst, particularly 5-35% wt. of nickel.

In the step of contacting the metal surface with the Group V compound and in the subsequent use of the modified metal, three main variables exist. These are (a) the Group V element used (b) the other element or radical of the Group V compound (c) the conditions of contacting and the subsequent conditions to which the metal is exposed.

The preferred Group V elements are phosphorus and antimony. Both are capable of giving catalyst of high activity and good selectivity. The degree of selectivity as between one or the other may vary depending on the other factors listed above and experiments may be necessary to determine which clement is preferred in any given situation.

The amount of the Group V element in relation to the Group III metal can be quite small seeing that only a surface treatment is necessary. Preferably the amount of Group V element is from 0.01 to 0.5 g.-atoms/ g. atoms of Group VIII element.

The other element or radical of the Group V compound is preferably an organic radical, particularly a hydrocarbon radical or an alkoxy radical. Thus it may be an alkyl, cycloalkyl or aryl radical or a combination of such groups e.g. an aralkyl radical. The radicals can be the same or different in any given compound. The radical may contain from l to 20 carbon atoms. The size of the radical has been found to have a signiiicant effect on the selectivity conferred. Without being bound by any theory it is suggested that the size of the element or radical determines the number of molecules that can be adsorbed onto a given area of metal surface and hence the spacing of the atoms of the Group V element on the metal surface. With a small radical the Group V atoms will be more closely spaced and the area of free metal surface between the Group V atoms correspondingly smaller.

When the Group V element is bismuth the preferred X radicals are methyl, ethyl, n-propyl, n-butyl or phenyl.

The Group V compound is readily adsorbed onto the metal surface and mild conditions can be used if desired for example atmospheric temperature (O50 C.) and 3 preferably atmospheric pressure. If desired the modified metal surface may be used catalytically under these conditions also. The compound may be used in liquid or vapour phase depending on its boiling point and either conversion of di-olens to mono-oleiis without conversion of mono-olens or aromatics if used under the same low temperature conditions. Catalysts prepared from Group V compounds containing organic radicals of small by itself or in an inert liquid or gaseous diluent. It may 5 size are more selective than catalysts prepared from Group be used with an inert saturated hydrocarbon diluent. V compounds with larger organic radicals under similar When the Group V compound is used under these conconditions. ditions it is believed that the whole compound is ad- Catalysts prepared under higher temperature or pressorbed and remains on the surface as the compound. sures tend to show selectivity for hydrogenation of di- More severe conditions can however be used for the 1o and mono-oleus to parafns, again without appreciable contacting or can be applied after the low temperature hydrogenation to aromatics. Again, the use of Group V contacting described above. Thus elevated temperatures compounds with small size organic radicals gives the of for example 50-250 C. and elevated pressures can more selective catalysts. be used simultaneously or subsequently. Again the com- Preferred feedstocks contain unsaturated non-aromatic pound can be in liquid or vapour phase and can have a hydrocarbons alone or in admixture with aromatics. Satliquid or vapour diluent. The diluent may be inert or it urated hydrocarbons may also be present. Suitable feedmay be a reducing gas such as hydrogen. Treatment in stocks are hydrocarbons or hydrocarbon mixtures having hydrogen is, in fact, preferred either simultaneously with 2-.20 carbon atoms, for example unsaturated petroleum the Contacting 0r Subsequently. It iS believed that at telllfractions. Preferably the feedstocks are sulphur-free. peratures of 50-250 C. and, preferably, under reducing 20 Suitable ranges of process conditions for thehydroconditions the Group V compound is decomposed leavgenaiion may be ing only the Group V element on the metal surface. If o the subsequent use to which the catalyst is put includes gemperatueoo .C' elevated temperature or pressure or reducing conditions, ressurep'slg' Space velocity-0.1-10 v./v./hr. 1t follows that the Group V compound will be decom- 25 H .HC 1 t. 01 20.1 posed in the early stages of the process. 2' m0 e ra lo The pressure used during the contacting or during sub- The invention is illustrated by the following examples. sequent treatment can be 0 to 1000 p.s.i.g. EXAMPLE 1 If desired, two or more treatments with the Group V l compound may be given. Preferably the Group V com- 3o A Catalyst WflS Prepared blf lmpregrta'tlrtg Sel21011te W 1th pound is dccoinposcd simultaneously with or subsequently a solution of nickel formate in ammonia solution to give to the first treatment, before the second treatment. a nickel eOrlterlt 0f 10% Wtand drylrlg at 120 C- The The temperature 0f the Second treatment may be l'llCkel formate WaS heIl reduced O Illekell at 375 C. to 250 C. or 0 to 50 C. In the latter case the catalyst for 4 hours irl a Stream 0f hydrogen Owlrlg at 1000 may be subsequently heated to 50 to 250 C. 35 V-/V-/hr The invention includes a process for converting organic Portions of this catalyst were then treated with various compounds, particularly for hydrogenating unsaturated COmPOUUdS 0f GrOUP V eterrlents and tested for hydro' Organic Compounds, comprising Contacting an Organic gel'lalOIl aCtlVlty and SeleCtlVlty. The feedStOCkS Were (il) compound under conversion conditions with a catalyst 10% V01- SOPrerle rl rl'hePtarle and (b) 10% V01- ben' prepared as described abovc 40 zene in cyclohexane. Feedstocks (a) and (b) were passed The invention further provides a process for hydro in succession over the catalysts. The hydrogenation procgenating unsaturated organic compounds which comprises eSS COIldtOIlS, Other the-r1 temperature, Were contacting an unsaturated organic compound under hypressure atmospheric drogenating conditions with a catalyst prepared as de- Space Velocitywz LHSV scribed above. 4o H ,HC 1 r ti0 8,1 As indicated earlier, the nature of the catalyst prep- 2' mo e a aration will affect the activity and particularly the selec- The Group V compounds used, the conditions of treattivity of the catalyst. Thus the catalyst prepared by conment with the Group V compound, the hydrogenation tacting the metal surface -at low temperatures of 0-50" C. temperature used and the results obtained are set out in has been found in most cases to have selectivity for the Tables l and 2 following:

TABLE i Group V compound used EtiP iiBugP n-oetylaP 3P Isopreiie Bcn- Isoprena Ben- Isoprenc Bcn- Isoprene Bcn ZORG Zelle Zeile ZEUS Activ- Selccactiv- Aetiv- Seleeactiv- Activ- Selecactiv- Activ- Selecactiv- Picti'eatiiient ity tivity ity ity tivity ity ity tivity ity ity tivity ity Catalyst l-XaP in n-dccane passed over 99 93 99 78 100 22 100 51 freshly reduced catalyst for 1 hour at room temperature C.). Hydrogenation at room temperature. Cataiystz-Cataiyst 1 heated in H2 nt 100 o 27 100 0 76.2 100 0 100 100 0 31.5

for l hour. Hydrogenation at CatalystD 3-Hrat Catalyst 2 to 100 C. in 100 o 25 100 0 S3 100 0 100 100 u 37.5

iii Hg l'or 1 hour and tlicn cool to 100 C. Hydrogcnation at 100 C.

Nora:

Isoprcno activity sopentane plus nictliyl buteiics X100 isopentane plus methyl butcnes plus isopi'ene cyclohexaiic cyclolicxane plus benzene) 10 Benzene activity- 0 TABLE 2 Group V compound used nBugSb 3Sb Isoprene Isoprene Pretreatment Activity Selectivity activity Activity selectivity activity Catalyst Lt-XaSb in n-decane passed over freshly reduced catalyst for 1 hour at room temperature. Hydrogenation at room tempera` ure 97 74 92 71 Catalyst -Catalyst 4 heated in H2 at 100 C. for 1 hour. Hydrogenation at 100 C 100 22 17 100 35 1S Catalyst -Heat Catalyst to 200 C. in H2 for 1 hour and then cool to 100 C. Hydrogenation at 100 C 100 6. 5 10 100 0 18 The results using Catalyst 1 of Table 1 show that when phosphiding and use occurs at room temperature the catalyst has selectivity for converting di-olelins to monooleiins, particularly when using tri-ethyl phosphine. The selectivity is in the order and is shown in FIG. 1.

Comparing the relative effects of phosphorus and antimony (i.e. comparing Catalyst 1 of Table 1 with Catalyst 4 of Table 2), there is little difference when using the tri-n-butyl compound, but a rather great difference when using the tri-phenyl compound.

The results of Catalyst 2 of Table 1 are similar to results with Catalyst 3 showing that heating at 100 C. or 200 C. makes little difference. These two catalysts convert isoprene to isopentane. Selectivity for olen hydrogenation without extensive aromatic hydrogenation occurs with the tri-ethyl and tri-phenyl compounds and the selectivity is and is shown in FIG. 2.

Comparing the relative effects of phosphorus and antimony (i.e. Catalysts 2 and 3 of Table 1 with Catalysts 5 land 6 of Table 2) it will be seen that benzene hydrogenation activity is less with the antimony compounds. The antimony compounds also show some selective di-oleiin hydrogenation activity. Here the difference between 100 and 200 C. for the catalyst treatment is signiicant.

The phosphorus content of these catalysts decrease in the order The phosphorus nickel atomic ratios for the catalysts of Table 1 were as follows:

EtaP 0.12621 n-Bu3P s 0.095:1 n-'Octyl3P 0.045:1

It will be noted that the smaller the organic radical the greater the amount of phosphorus adsorbed.

For the three alkyl phosphine treated catalysts there is a direct relationship between selectivity to methyl hutenes and phosphorus content. This is shown in FIG. 3.

EXAMPLE 2 Catalyst 2 of Example 1 was rephosphided with triethyl phosphine and then tested for hydrogenation activity as in Example 1. The treatment conditions, the hydrogenation temperature and the results obtained are Table 3 shows that the rephosphiding increased the selectivity of the catalyst for hydrogenating isoprene to isopentane without hydrogenating benzene, without adversely aiecting the activity.

EXAMPLE 3 Further portions of the 10% wt. nickel-sepiolite catalyst of Example l were phosphided with triethyl phosphine at elevated temperature in hydrogen (i.e. so that there was simultaneous adsorption and decomposition of the phosphine). The catalysts, designated Catalysts 8 and 9 were tested for hydrogenation activity as in Example l. The treatment conditions, the hydrogenation temperature and the results obtained are shown in Table 4 below.

EXAMPLE 4 A catalyst was prepared in the same way as Catalyst 8 and was left overnight in an atmosphere of hydrogen at C. It was then tested for hydrogenation activity using as feedstock a mixture of 25% volume isoprene and 75% volume benzene. The process conditions were 120 C. atmospheric pressure and a hydrogen rate of 500 GHSV. The feedstock space velocity was varied during the run. The results obtained are shown in Table 5 below.

TABLE 5 Space Isoprene velocity Benzene Hours on stream (v./v./hr.) Activity Selectivity activity Table 5 shows the high activity and the low selectivity of the catalyst which was maintained over an extended period. The catalyst was left to stand overnight in hydrogen at 100 C. twice during the run so the total time of contact of the catalyst with hydrogen was considerably greater than the hours on stream shown.

EXAMPLE S Catalysts 10 to 12 were prepared as described in Table 6 and tested for isoprene hydrogenation. The results show` that the fully reduced nickel-on-sepiolite, pretreated with either triethyl or tri-n-butyl phosphine at room temperature hydrogenates isoprene under ambient conditions to a product rich in a-olens. In contrast, the sulphided nickel sepiolite (catalyst l2) produces an equilibrium distribution of oleiins containing mainly 2methyl butene- 2 under similar conditions. Catalyst 12 does not form part of the present invention and is included for cornparative purposes only.

TABLE 0,-T1IE EFFECT OF CATALYST PRETREATMENT 0N THE DISTRIBUTION OF METHYL BUTENES FROM ISOPRENE AT ROOM TEMPERATURE Test conditions: Feed-10 percent v./v. lsporene in n-heptane; Temperature-20 C.; Ieed new rate- 2 LHSV; Hf flow rate-750 GI-ISV.

Isoprene hydrogenation Methyl butcncs isomer distrubtuion (percent) (percent) Hours C C on Selec l l Pretreatment Stream Activity tivity C-C-C:C CC-C=C C-C=C-C Catalyst 10. Pass a solution oi EtgP in n-heptane over fullyre- 0-0. 5 99 92 14.3 44.0 41. 7 duced catalyst for one hour at room temperature. 2. 5-3 100 81 8.4 42.4 49.2 Test at room temperature. 5-5. 5 100 74 1.0 45. 0 53. 9 Catalyst 11. Pass a 5% solution of EtgP in n-heptane over the cata- 6. 5-7 74 99 22. 1 35. 9 42. 0 lyst at roem temperature. Test at room tempera- 8. 5-9 100 8!) 15. 2 41.0 43.8 ture. 10-11 100 87 12. 8 41. 3 45. 9 Catalyst 12. Pass a 5% solution of thiophen in n-decane over iully- {0-0. 5 100 97 0.2 11.0 88.8 reduced catalyst for 1.5 hours at room temperature. 4-4. 5 100 9S 1. 4 14. 7 83. 'J Test at room temperature. Thermodynamic equilibruim values at 27 C 0. 2 11.0 S8. 8

EXAMPLE 6 `Catalysts 13 and 14 were prepared and tested as described in Table 7. Catalyst 14 demonstrates the improvement in selectivity obtained by repeating the treatment with tri-n-butyl phosphine.

where M is phosphorus at least one of the X radicals may be R2P(CH2)- or TABLE 7 Test conditions: Feed-10 percent v./v. isoprene in n-hcptane; Temperature-20 C.; Feed flow rate-2 LH SV; Hzllow rate-750 GHSV.

Isoprene hydrogenatlon Selec- Methyl butenes isomer distribution tivity (percent) Hours to mono n olefms on Activity oleiins x 100 B-methyl 2-methyl 2-meth yl Pretreatment stream (percent) (percent) tota 01 115 butene-l butene-1 butene-2 Catalyst 13Soak 5 ml. offully-reduced nickel-on-sepiolite in 2-21/2 100 75 4G 4. 8 41.3 53. 7 m1. oi a 4.9 percent solution of nBurP in n-heptane for 1 33% 100 79 48 5. 5 42. 1 52. 4 hour. Drain oi the solution and wash the catalyst with ml. of n-hcptanc. Stood for 16 hours in Hz l-ll/g 100 00 54 13. 6 40. 7 45. 7 2-226 100 88 54 13. 2 40. 4 46. 4 Catalyst 14-Heat the catalyst at 100 C. overnight in hydrogen. Cool to room temperature and retreat with Stood for 64 hours in H2 nBuaP as above.

EXAMPLE 7 A platinum exchanged silica catalyst (catalyst 15) was prepared and tested as described in Table 8.

where n is zero or an integer from 1 to 20 and where R is a C1 to C20 hydrocarbon radical, the amount of the Group V compound being from 0.01 to 0.5 g.-atoms/g. atom of Group VIII metal.

TABLE S Test conditions: Feed-l0 percent v./v. isoprcne in n-heptane; Temperature-100 C.; Feed iiow rate-2 LHSV; Hz Ilow rate-450 GHSV.

Isoprcne hydrogenation Selec- Methyl butenes isomer distribution H t tivlty (percent) ours o mono on Activity olens am-X100 3-methyl 2methyl 2-methy1 Pretreatment stream (percent) (percent) total Ole'ls butene-l butene-l butene-2 Catalyst 15-Soak 5 ml. of 3 percent Weight platinum exchanged silica (previously reduced) with 30 ml. of a 4.9 %1 5G 77 G0 18. 3 41.3 40.4 percent solution of nBuiP in n-heptane for 1 hour. Drain oi the solution and wash the catalyst with 30 m1. of n- LV2-2% 55 75 62 19.4 42.8 37.8 heptane. Raise the temperature to 100 C.

Untreated reduced catalyst 0-3 100 0 What we claim is:

1. A method of preparing a catalyst which method comprises contacting a Group VIII metal surface of nickel or platinum with a compound of an element of Group V at a temperature in the range 0 to 250 C. so that the Group V element or compound is adsorbed onto the metal surface, the Group V compound having the general formula X3M where X is an organic radical containing from 1 to 20 carbon atoms, said radical being alkyl, cycloalkyl, alkoxy, aryl or combinations of such radicals, the X radicals being the same or different, and M is an atom of phosphorus, arsenic or antimony; and in the case 6. A method according to claim 1 wherein the Group V compound is contacted with the metal surface at 0 to 50 C.

7. A method according to claim 1 wherein the Group V compound is contacted with the metal surface at a temperature of 50 to 250 C. to decompose the Group V compound.

8. A method according to claim 7 wherein the catalyst is subsequently heated to from 50 to 250 C. to decompose the Group V compound.

9. A method according to claim 7 wherein the treatment at 50 to 250 C. is carried out in the presence of hydrogen. v

10. A method according to claim 7 wherein the catalyst is given one or more further treatments with the Group 15 compound at 50 to 250 C. or at 0 to 50 C. with subse- 20 quent heating to 50-250 C.

References Cited UNITED STATES PATENTS Barry 260-677 H Lindlar 260-677 H Weber 252-441 X Zajcew 252-472 X Silverman 252-437 Silverman 252-437 Rylander et al. 252-472 X Fenton 252-431 P X Dunning et al. 252-431 P X Shryne et al 252-431 P X PATRICK P. GARVIN, Primary Examiner U.S. Cl. X.R.

y CERTIFICATE OF CORRECTION ment N 3.642.658 y Dated Februarv l5- 1972 Inventot(s) Allum et al.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

column 2, line 3a, Catalysr' shuid be catalysts- Column 2, line 11, Group lll" should be #Group vill". Column l, line 8, "temperature" should be -temperatures. Column 5, line 2li, "great" should be --greater-.

Column 5, line 26, "of" should be "with",

Column 8, Table 6, 5th entry under C-CC=C, "41.0 should be /+O.

Claim 8, Claim 7" should be --Claim 6.

Claim l0, heatings" should be heating,

Signed and sealed this 12th day of September 1972.

(SEAL) Attest:

EDWARD M.lLETCHER,JR.l ROBERT GOTTSCHALK Attest-ing Officer Commissioner of Patent 

